go/pointer: clarify a comment
go/pointer: clarify a comment

Change-Id: Ia434ca4e7259cdb9a6f50d51432977fd31be27db
Reviewed-on: https://go-review.googlesource.com/21391
Reviewed-by: David Crawshaw <a2f0bf29257797dd66800b4fbb9945c3e216c004@golang.org>

syreclabs/go-tools,golang/tools,syreclabs/go-tools,golang/tools,syreclabs/go-tools,golang/tools,syreclabs/go-tools,golang/tools,syreclabs/go-tools,syreclabs/go-tools,golang/tools